Gas separation is an emerging technology with a rapidly developing market comprising applications like air separation for oxygen or nitrogen enrichment as well as acid gas removal and hydrocarbon recovery from natural gas streams. The economics of a membrane-based separation system depend on the gas permeability (thickness- and pressure-normalized flux) and selectivity (preferential permeation of one gas over another) of the material used. Unfortunately, there is a conventional trade-off between these two main parameters such that an increase in permeability is concurrent with a decrease in selectivity, and vice versa. This results in what is commonly referred to as an “upper-bound” to performance which is defined by polymeric materials with the highest known combinations of permeability and selectivity. It is revised to accommodate discoveries of better performing polymers and is therefore taken as a gauge of the state-of-the-art.
Polyimides are one dominant class of polymers developed by major competitors in the membrane-based gas separation industry for a range of gas separation applications including air separations (oxygen/nitrogen enrichment) and hydrogen separations (hydrogen recovery from ammonia purge-gas streams) as well as the removal of acid gases (CO2 and H2S) and higher hydrocarbons (C2+) from natural gas. Polyimides, typically formed by the polycondensation reaction between a diamine and dianhydride followed by the cyclodehydration step, have a versatile structure amenable to simple, systematic changes. They are well known as high performance polymers which possess high thermal and chemical stabilities, good mechanical and superior film-forming properties. However, current polyimides do not address current gas separation needs, and therefore, new polyimides are desirable.
Discussion
Before the present disclosure is described in greater detail, it is to be understood that this disclosure is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present disclosure will be limited only by the appended claims.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit (unless the context clearly dictates otherwise), between the upper and lower limit of that range, and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described.
All publications and patents cited in this specification are herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure. Further, the dates of publication provided could be different from the actual publication dates that may need to be independently confirmed.
As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order that is logically possible.
Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of chemistry, synthetic organic chemistry, polymer chemistry, analytical chemistry, and the like, which are within the skill of the art. Such techniques are explained fully in the literature.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to perform the methods and use the compositions and compounds disclosed and claimed herein. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C., and pressure is in bar. Standard temperature and pressure are defined as 0° C. and 1 bar.
Before the embodiments of the present disclosure are described in detail, it is to be understood that, unless otherwise indicated, the present disclosure is not limited to particular materials, reagents, reaction materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequence where this is logically possible.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a support” includes a plurality of supports. In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings unless a contrary intention is apparent.
Definitions:
The term “substituted” refers to any one or more hydrogens on the designated atom that can be replaced with a selection from the indicated group, provided that the designated atom's normal valence is not exceeded, and that the substitution results in a stable compound.
As used herein, “alkyl” or “alkyl group” refers to a branched saturated aliphatic hydrocarbon. Examples of alkyl include, but are not limited to iso-propyl, sec-butyl, t-butyl, and iso-pentyl.
The term “substituted,” as in “substituted alkyl”, “substituted aryl,” “substituted heteroaryl” and the like means that the substituted group may contain in place of one or more hydrogens a group such as alkyl, hydroxy, amino, halo, trifluoromethyl, cyano, —NH(lower alkyl), —N(lower alkyl)2, lower alkoxy, lower alkylthio, or carboxy, and thus embraces the terms haloalkyl, alkoxy, fluorobenzyl, and the sulfur and phosphorous containing substitutions referred to below.
As used herein, “halo”, “halogen”, or “halogen radical” refers to a fluorine, chlorine, bromine, and iodine, and radicals thereof. Further, when used in compound words, such as “haloalkyl” or “haloalkenyl”, “halo” refers to an alkyl or alkenyl radical in which one or more hydrogens are substituted by halogen radicals. Examples of haloalkyl include, but are not limited to, trifluoromethyl, trichloromethyl, pentafluoroethyl, and pentachloroethyl.
The term “aryl” as used herein, refers to an aromatic monocyclic or multicyclic ring system of about 6 to about 14 carbon atoms, preferably of about 6 to about 10 carbon atoms. Exemplary aryl groups include phenyl or naphthyl, or phenyl substituted or naphthyl substituted.
The term “heteroaryl” is used herein to denote an aromatic ring or fused ring structure of carbon atoms with one or more non-carbon atoms, such as oxygen, nitrogen, and sulfur, in the ring or in one or more of the rings in fused ring structures. Preferred examples are furanyl, imidazyl, pyranyl, pyrrolyl, and pyridyl.
General Discussion
Embodiments of the present disclosure provide for a triptycene-based monomer, a method of making a triptycene-based monomer, a triptycene-based aromatic polyimide, a method of making a triptycene-based aromatic polyimide, methods of using triptycene-based aromatic polyimides, structures incorporating triptycene-based aromatic polyimides, methods of gas separation, and the like. Embodiments of the triptycene-based aromatic polyimides have one or more of the following characteristics: intrinsic microporosity, good thermal stability, and enhanced solubility. Intrinsic microporosity is defined herein as a polymeric material with pore sizes of less than 2 nm and a surface porosity of >100 m2/g, as determined by nitrogen adsorption method at 77 K. Attachment A includes exemplary reactions schemes and gas separation data for an embodiment of a triptycene-based aromatic polyimide.
Embodiments of the triptycene-based monomers and triptycene-based aromatic polyimides are expected to be economically attractive compared with the current polymer-based membranes due to their high permeabilities and excellent selectivities. Higher permeability offers savings in capital cost of membrane systems by reducing area requirements to handle a given process flow. It also reduces energy consumption by reducing compression requirements. Higher selectivity introduces large savings by reducing crossover of valuable gas feed components into the permeate streams and also by reducing the need for multi-stage systems.
In an exemplary embodiment, a triptycene-based aromatic polyimide can be used to form a gas separation membrane. The membrane can have exceptional performance for gas separation applications significantly transcending the upper bounds. Specifically, embodiments of membranes incorporating the triptycene-based polyimide provide unprecedented performance in gas separation applications including nitrogen enrichment and hydrogen recovery from ammonia purge-gas streams. In addition, embodiments of membranes incorporating the triptycene-based polyimide have excellent performance in olefin/paraffin (C3H6 C3H8) and natural gas sweetening (CO2/CH) applications.
In an exemplary embodiment, triptycene-based aromatic polyimides are microporous and have the highest BET surface area (e.g., up to 850 m2/g) of all previously reported non-network polyimides, as conventionally measured by the area accessible to N2 molecules at 77K. The microporosity and the good solubility (processability) of these materials appears to have resulted from the incorporation of the rigid three-dimensional structure of a triptycene moiety, which prevents the close packing of the polymer chains and decreases the interchain interactions. Embodiments of these polyimides demonstrate performance significantly transcending the upper-bounds for important gas separation applications. In particular, exemplary embodiments of the triptycene-based aromatic polyimides when used in gas separation membranes demonstrate unprecedented combinations of permeability and selectivity in air separations (i.e., O2/N2 in nitrogen enrichment), hydrogen separations (i.e., H2/N2 and H2/CH4 for hydrogen recovery from ammonia purge gas streams), and challenging olefin/paraffin separations (i.e., C3H6/C3H8). Furthermore, these materials show excellent performance relative to the upper-bound for CO2/CH4 separations (natural gas sweetening). Attachment A includes data that describes the gas separation properties of membranes made from the triptycene-based aromatic polyimide of the present disclosure.
In addition, due to their good solubilities, thermal and chemical stabilities, and high microporosities, these materials can be implemented in a wide range of industrial applications related to thermally stable coatings, low dielectric constant films, optoelectronic materials, sensors, and gas storage media.
In an exemplary embodiment, the triptycene-based aromatic polyimide can be made using a triptycene-based monomer as shown in the following structure:
In an embodiment, AR can be a substituted or un-substituted aromatic moiety. In an exemplary embodiment, the substituted or un-substituted aromatic moiety can be: a substituted or un-substituted aryl group, a substituted or un-substituted heteroaryl group. In an embodiment, AR can be one of the groups shown in Scheme 2.
In an embodiment, R1 and R2 can each independently be hydrogen or a substituted or non-substituted alkyl group. In particular, R1 and R2 can each be independently substituted or un-substituted branched C3 to C5 alkyl groups.
Representative triptycene-based monomers can have the following structures:

In an exemplary embodiment, the triptycene-based monomer can be synthesized using the synthesis described in Scheme 1 in Attachment A. Although some specific solvents, acids, and other reagents are described, other suitable solvent, acids, and reagents can be used if they accomplish the same purpose. R can include the same groups as R1 and R2.
In an exemplary embodiment, the triptycene-based aromatic polyimide can include a compound as represented by the following structure:

In an embodiment, n can be 1 to 10,000. In an exemplary embodiment, X can be a triptycene-based monomer as describe above. In an exemplary embodiment, Y can be a divalent organic group. In an embodiment, Y can be represented by AR′, where AR′ can be a group as described in Scheme 2, Attachment A. AR′ corresponds to the base of various diamines that can be used to form the polyimide. In an embodiment, the divalent organic group is selected from the group consisting of: a substituted or un-substituted aryl group, a substituted or un-substituted heteroaryl group.
Representative triptycene-based aromatic polyimides can have the following structures:

In an exemplary embodiment, the triptycene-based aromatic polyimide can be synthesized by reacting the triptycene-based monomer with a multi-amine. In an embodiment, the multi-amine can include a diamine, triamine, tetramine, and an amine having 5 or more amino groups.
An exemplary embodiment of a synthesis can include the reaction scheme shown below:

AR, R1, and R2 have the same meaning as described above. DA is a linking group derived from the diamine. In an embodiment, the diamine can include those described in Schemes 2 and 3. In an embodiment, DA can include AR′, as described in Scheme 2.
In another embodiment, the triptycene-based aromatic polyimide can be synthesized by reacting the triptycene-based monomer with a triamine or multi-amine. In this embodiment, an insoluble microporous network of polyimides can be formed that can be used for gas storage (e.g., H2, CO2, CH4, and the like). An exemplary reaction scheme is shown in Scheme 5.
In another embodiment, a polypyrrolone can by synthesized by reacting the triptycene-based monomer with a multi-amine. An exemplary reaction scheme is shown in Scheme 4.
As mentioned above, polyimides of the present disclosure can be used to form membranes that can be used in gas separation. The membranes including the polyimides can be formed using conventional techniques.
As mentioned above, the membranes of the present disclosure can be used in conventional gas separation systems such as systems to enrich a specific gas content in a gas mixture (e.g., oxygen enrichment, nitrogen enrichment, and the like). In addition, the membranes can be used in hydrogen gas separations.
In general, a first gas is separated from a first gas mixture with a membrane of the present disclosure to form a second gas mixture that is enriched in one or more components of the first gas mixture. In an embodiment, the result can be the separation of a gas(es) from another gas(es) such as in oxygen/nitrogen, hydrogen/methane, hydrogen/nitrogen, carbon dioxide/methane, carbon dioxide/nitrogen, hydrogen/C2+ hydrocarbons, hydrogen sulfide/methane, carbon dioxide/hydrogen sulfide, ethylene/ethane, propylene/propane, water vapor/hydrocarbons, C2+/hydrogen, C2+/methane etc.